This test method determines the open-hole compressive strength of sandwich constructions in a direction parallel to the sandwich facesheet plane. Permissible core material forms include those with continuous bonding surfaces (such as balsa wood and foams) as well as those with discontinuous bonding surfaces (such as honeycomb). This test method consists of subjecting a sandwich panel, with a centrally located hole, to monotonically increasing compressive force parallel to the plane of its faces. The specimen is installed in a multi-piece support fixture, that has been aligned to minimize loading eccentricities and induced specimen bending. The specimen/fixture assembly is placed between flat platens and end-loaded under compressive force until failure. Applied force, crosshead displacement, and strain data are recorded while loading. Ultimate strength is calculated based on the nominal cross-sectional area of the two facesheets, disregarding the presence of the hole. While the hole causes a stress concentration and reduced net section, it is common aerospace practice to develop notched design allowable strengths based on gross section stress to account for various stress concentrations (fastener holes, free edges, flaws, damage, and so forth) not explicitly modeled in the stress analysis.
composite materials; sandwich composites; sandwich construction; open-hole compressive strength; compression testing
The proposed test method is used to determine the open-hole (notched) strength of a composite sandwich panel. Results may be used for structural design allowables, material specifications, research and development, and quality assurance. it is common aerospace practice to use the notched strength results from this test method to account for various stress concentrations (fastener holes, free edges, flaws, damage, and so forth) not explicitly modeled in stress analyses. Note that this proposed test method is analogous to ASTM D6484, an existing standard test method for open-hole compressive strength of polymer matrix composite laminates. However the proposed test method is to be used for sandwich composites.
The title and scope are in draft form and are under development within this